The invention relates generally to an interface within a computer system between two different protocols. The invention deals more particularly with a control unit which provides a universal interface between a variety of I/O protocols and another computer protocol.
A computer protocol is a set of systematic and syntactic rules that define the manner of communication between two components. For example, in IBM Corporation's system network architecture (SNA), the protocols define the meanings of and sequencing rules for requests and responses used for managing the network, transferring the data and synchronizing the states of network components.
In many types of computer systems, a main computer communicates with a variety of peripheral devices. For example, in IBM Corporation's 9370 Computer System, ("9370" is a trademark of IBM Corporation) a computer communicates with a variety of I/O devices such as printers, DASD storage devices, personal computers, etc. This communication is sometimes made via a token ring adapter and token ring network or an ethernet adapter and ethernet network. Heretofore, a different control unit was provided between a channel of the main computer and each such adapter in the aforesaid example. In other computer systems, a different control unit was also provided between the main computer channel and each adapter for the peripheral devices. The need for the different control units complicated the design, and the addition of new peripheral devices required the development and installation of new control units.
Also, in the aforesaid 9370 system, the System 370 protocol was more complicated than necessary for the token ring or ethernet adapters, i.e. they provided more options and functions than required, and more steps and fields to implement. Moreover, in this system, the channels and control units were separated from the System 370 computer by a cable, and this separation required safeguards which added to the complexity of the system.
Accordingly, a general object of the present invention is to provide a control unit for a computer communication interface, which control unit is universally applicable to a variety of different I/O devices or adapters therefor.
Another general object of the present invention is to provide a control unit of the foregoing type which provides a less complicated interface to the I/O devices or adapters than required for the main computer channel.
A more specific object of the present invention is to provide a control unit of the foregoing type which is usable between a System 370 main computer and a token ring adapter, an ethernet adapter or other I/O devices.
Another specific object of the present invention is to simplify the interface between the control unit and the main computer.